In change-speed gearboxes for motor vehicles, the rotation direction reversal of the drive output shaft required for reversing the vehicle is usually produced by an intermediate gearwheel arranged on an intermediate shaft in the gearbox housing. This intermediate gearwheel is then subjected to particularly large loads since it meshes simultaneously with two associated gearwheels, on the one hand with an associated gearwheel of the drive input shaft or countershaft, and on the other hand with a gearwheel of the drive output shaft.
This high loading of the intermediate gearwheel results in severe stressing of the intermediate shaft and the mountings of the intermediate shaft, and ultimately also of the gearbox housing in the area of the bearing points. To counteract pronounced deflection of the intermediate shaft, which would otherwise lead to flank-line deviations in the meshing of the intermediate gearwheels, and in order to withstand the high loads, the gearbox housing must have high strength in the area of the intermediate shaft.
A change-speed transmission with a transmission housing of this type is known from DE 103 16 321 A1, in which an intermediate shaft with an intermediate gearwheel for producing a rotation direction reversal of the drive output shaft is located in a main chamber and parallel to the axes of the drive input and drive output shafts. In this case the intermediate shaft is located on one side in a recess of the transmission housing and on the other side it is secured on the transmission housing by a half-shell and bolted joint. As a whole, the intermediate shaft with its intermediate gearwheel is arranged in a bulge of the transmission housing.
A disadvantage of such an arrangement is that the manner of fixing the intermediate shaft in the transmission housing, in contrast to mounting the shaft in massive walls of the transmission housing, is characterized by lower strength. Furthermore, to produce the bulge in the main chamber which accommodates the intermediate shaft correspondingly more material is used, and this ultimately also increases the manufacturing cost and effort.
Furthermore, from DE 198 11 874 C2 a change-speed transmission with a transmission housing is known, in which the intermediate shaft with its intermediate gearwheel are located in a rectangular auxiliary chamber positioned laterally on the main chamber. In this case there is an aperture between the main and the auxiliary chambers, through which the intermediate gearwheel is in contact with the two associated gearwheels, respectively of the drive input and drive output shafts. To position and mount the intermediate gearwheel in the auxiliary chamber, the auxiliary chamber has a rectangular opening which is sealed by a bolted-on cover once assembly has been completed.
Such an arrangement has the disadvantage that the rectangular cross-section of the auxiliary chamber results in notch stresses in this housing area, this effect being reinforced still more by the threaded bores of the cover. Moreover, the bolted attachment of the housing cover results in additional manufacturing cost and effort.